Method async

src/brpc/span.h:182–182

    int64_t start_send_real_us() const { return _start_send_real_us; }
    int64_t sent_real_us() const { return _sent_real_us; }
    bool async() const { return _async; }
    const std::string& full_method_name() const { return _full_method_name; }
    
    // Returns a copy instead of a reference for thread safety.